Problem: A 6 cm by 8 cm rectangle is inscribed in a circle. What is the number of centimeters in the circumference of the circle? Express your answer in terms of $\pi$.

[asy]import graph;
defaultpen(linewidth(0.7));
draw(Circle((0,0),20));
draw((-16,-12)--(16,-12)--(16,12)--(-16,12)--cycle);
[/asy]
Draw a diagonal of the rectangle.  By the Pythagorean theorem, the length of the diagonal is $\sqrt{6^2+8^2}=10$ centimeters.  Also, by symmetry the diagonal of the rectangle is a diameter of the circle.  The circumference of the circle is $\pi\times (\text{diameter})=\boxed{10\pi}$ centimeters. [asy]
import graph;
defaultpen(linewidth(0.7));
draw(Circle((0,0),20));
draw((-16,-12)--(16,-12)--(16,12)--(-16,12)--cycle);
draw((16,-12)--(-16,12));
draw(rightanglemark((16,-12),(16,12),(-16,12),45));[/asy]